There are many applications in which it is required to transfer a substance from a container, in which the substance is supplied, to a supply point of a system in which the substance is to be processed or used, without permitting spillage or contamination of the substance. This may either be because the substances themselves or associated fumes are hazardous to operating personnel, or because the substances, such as foodstuffs, are to be kept free from contamination from the outside.
International Patent Publication No. WO 89/11219 discloses an agricultural sprayer system of a type which includes a reservoir for supplying a dilutant for mixing with a chemical concentrate, and a spray head for spraying a mixture of the dilutant and the concentrate. The concentrate is supplied in a container and requires to be diluted with the dilutant, generally water, prior to use, the container being subsequently rinsed out with dilutant. In order to obviate the hazard to the operator due to possible chemical concentrate spillage on transfer from the container to the sprayer system, the system includes a supply cap and associated hose for attachment to the outlet of the container to permit supply of concentrate to the system is a sealed manner when the container is inverted so that the outlet is at its bottom.
The known supply cap includes an outlet duct for supply of concentrate from within the container when the container is inverted, a valved inlet duct for the passage of air into the container during supply of concentrate through the outlet duct, and an associated float provided to ensure that, when the container is filled with rinsing solution, the valved inlet duct is closed off by the float when the level of solution reaches the height of the float in the container. However such a supply cap is complicated in construction and does not completely obviate the hazard to the operator due to possible concentrate spillage when the cap is being fitted to the container after removal of the closure with which the container is supplied.
It is an object of the invention to provide an improved supply cap for this purpose.